The objective of the proposed research is to elucidate the mechanisms which regulate the quantity and quality of phospholipids present in biological membranes. A biochemical-genetical approach on the regulation of membrane phospholipid synthesis in Escherichia coli will build from several mutants defective in membrane phospholipid biosynthesis. The mechanism of sn-glycerol 3-phosphate inhibition of highly purified preparations of wild type and feedback resistant sn-glycerol 3-phosphate dehydrogenases will be investigated by performing sn-glycerol 3-phosphate binding studies. These data, along with steady state kinetics seek to establish the existence of an allosteric, regulatory site for sn-glycerol 3-phosphate, which functions to regulate the biosynthesis of sn-glycerol 3-phosphate. Hybrid plasmid bearing the plsB and bpsA genes will be employed. The plsB gene product, the sn-glycerol 3-phosphate acyltransferase will be solubilized from membranes prepared from the hybrid plasmid bearing strains with Triton X-100. Attempts will be made to stabilize and purify the enzyme to homogeneity. The purified glycerol-P acyltransferase will be characterized physically, chemically, and kinetically. Studies will focus on whether one enzyme utilizes acyl-CoA and acyl-ACP substrate, and on reconstitution of activity with phospholipids. These studies on two enzymes which function in membrane phospholipid biosynthesis should provide useful information about the regulation of membrane phospholipid synthesis, and membrane biogenesis. The regulation of lipid synthesis appears to be of significance to cancer, obesity, atherosclerosis, and to understanding the role of phospholipids in the structure and function of biological membranes.